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From: Dmitry Antipov <dmantipov@yandex.ru>
To: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: linux-bluetooth@vger.kernel.org,
	Dmitry Antipov <dmantipov@yandex.ru>
Subject: [PATCH] [RFC] Bluetooth: fix race condition in sco_connect()
Date: Wed,  3 Apr 2024 17:27:06 +0300
Message-ID: <20240403142706.25748-1-dmantipov@yandex.ru>
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This patch is intended to fix the race condition between two
'sco_connect()' calls, where two instances of 'struct sco_conn'
are erroneously set up to share the pointer to the same 'struct
sock'. When one of the connections goes away, it destroys an
underlying socket as well, leaving dangling pointer to destroyed
socket within another. Next, if the latter (alive) connection
enters 'sco_sock_timeout()', an attempt to do 'lock_sock()' on
a destroyed socket causes use-after-free write reported by KASAN
at https://syzkaller.appspot.com/bug?extid=4c0d0c4cde787116d465.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
---
 net/bluetooth/sco.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 43daf965a01e..f8e5e4c3420f 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -228,7 +228,7 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk,
 	int err = 0;
 
 	sco_conn_lock(conn);
-	if (conn->sk)
+	if (conn->sk || sco_pi(sk)->conn)
 		err = -EBUSY;
 	else
 		__sco_chan_add(conn, sk, parent);
-- 
2.44.0